The present invention relates generally to cardiac stimulation leads, and more particularly to an implantable cardiac leads including an electrode and a reduced diameter lead body.
Implantable leads form an electrical connection between a pulse generator or other electronic device and a tissue or structure in the body. For example, leads transmit electric signals used to stimulate cardiac or nerve tissue in one direction and signals generated by sensors placed in proximity to particular organs or tissues in the opposite direction. Leads typically include one or more electric elements at the lead""s distal end. The electric elements are designed to form an electrical connection with a tissue or organ. Most leads also include a lead connector pin at the lead""s proximal end. Lead connector pins are adapted to electrically and mechanically connect leads to the pulse generators or other electronic medical devices. A flexible conductor connects the electric element to the lead connector pin. Commonly, the flexible conductor takes the form of a single or multifilar wire coil, although, there is an increasing interest in using stranded cables as conductors. Regardless of the form, a layer of insulating material typically surrounds the flexible conductors. Together, the flexible conductor and the insulating layer form the lead body. The lead body couples the lead connector pin at its proximal end with the electric element at its distal end.
Leads are implanted in the cardiovascular system, typically through a vein, to confer a stimulus to a specific location within the heart. The introduction of a lead into the vein and heart necessarily at least partially obstructs blood flow. In addition, the diameter of the lead can reduce the efficiency of valve function in the heart and veins. Blood flow and valve obstruction problems increase when a patient""s treatment requires the implantation of multiple leads. The placement of a conventional, prior art pacing lead in individuals suffering from ischemia can further exacerbate the individual""s problems. Thus, despite the many advantages associated with endocardial leads, there has always been a tradeoff associated with their use in many patients.
The degree of blood vessel obstruction is a function of a lead body""s diameter. Thus, reducing lead body diameter will reduce the degree of obstruction. This can be extremely important with children. Children are inherently more susceptible to having blood flow obstructed because many of their blood vessels are simply too small to accommodate conventional implantable leads. Further complicating their situation, children are often the least able to adjust to a diminished blood flow or impaired valve function. In a similar fashion, adult patients with occluded vessels or impaired valves are also susceptible to having their blood flow obstructed. These adult patients may not be suitable candidates for transvenous implanted leads because of the diameter of currently available leads. Thus, a need exists for a reduced diameter lead body to minimize the obstruction to blood flow from intravenously implanted leads.
Conventional lead designs have several disadvantages. Typical methods for lead implantation require that the lead body receive a stylet. Conventional lead bodies have an internal lumen that is coextensive with the lead body to accommodate the stylet. The stylet enables the lead to be steered within the vessels to a target location in the heart. This internal lumen adds to the lead""s diameter. The lumen""s diameter often constitutes a significant portion of the overall diameter of the lead body. Similarly, conventional lead bodies often incorporate coiled conductor wires. The coiling necessarily doubles the wires diameter and typically creates a central lumen along the coil""s axis. For the above reasons, the smallest available conventional leads may still be too large for successful transvenous implantation in some patients. Thus, a need exists for a method for implanting a lead having a reduced size lead body.
In addition, when multiple conventional leads are introduced into a patient there is a tendency for the leads to abrade one another and the tissue of the patient due to the rigidity of the lead bodies. The inter-lead abrasion reduces the life of the lead and increases the frequency of surgery to replace the worn leads. The lead body to tissue abrasion can traumatize the tissues of the circulatory system. Thus, a need exists for a lead having better flexibility to reduce the effects of abrasion. Finally, conventional tissue stimulating leads also require a relatively large amount of raw material for their manufacture. This increases production costs. Thus, a need exists for a lead requiring less raw material for manufacture.
The present invention meets the above needs and provides additional advantages and improvements that will be evident to those skilled in the art. The present invention provides an improved lead having a reduced diameter lead body and a method for implanting the lead within the heart.
In a first aspect of the invention, the lead includes an electrode assembly having a stylet guide and a reduced diameter lead body. The reduced diameter lead body electrically is coupled to the electrode assembly. The electrode assembly defines the stylet guide that is configured to guide a stylet into a position at a proximal end of the electrode assembly during implantation. The stylet guide may include a conical surface. The stylet guide enables the electrode assembly to be easily pushed through a guide catheter. The stylet guide eliminates the need to have a lead body capable of receiving a stylet and hence allows for the reduced diameter lead body. The distal end of the electrode assembly can include a cavity configured to removably secure a distal end of a pushing stylet. Including such a cavity enables the pushing stylet to be better maintained on the electrode assembly during implantation. The reduced diameter lead body may include a cable or coil conductor and an insulator. The electrode assembly may be of a passive fixation or an active fixation design. If the electrode assembly uses passive fixation, the assembly may include at least one tine to fix the electrode at a target location. If the electrode assembly uses active fixation, the assembly may include a screw helix as is known in the art.
The method for implanting a lead conforming to the first aspect of the present invention includes a guide catheter and a pushing stylet. The distal end of the guide catheter is positioned at a target location within the heart of a patient. The guide catheter may include a radio-opaque coating allowing the catheter to be visualized during positioning using fluoroscopy, magnetic resonance imaging, echocardiography, or by other methods known to those skilled in the art. The electrode assembly is placed within the guide catheter""s lumen at the proximal end of the guide catheter. The stylet guide is oriented to receive the distal end of the pushing stylet. The pushing stylet is passed through the proximal end of the guide catheter. In doing so, the distal end of the pushing stylet abuts the proximal end of the electrode assembly and thereby pushes the electrode assembly through the catheter to the target location in the patient""s heart. Once the electrode assembly is at the target location, it is secured to the target location. Once secured the pushing stylet and catheter are withdrawn from the heart.
In a second aspect of the invention, the lead includes an electrode assembly having a cavity and a reduced diameter lead body. The cavity is configured to frictionally engage a distal end of a pushing stylet. This configuration allows the electrode assembly to be guided through a catheter to a target location with the pushing stylet. Thus, the cavity eliminates the need to have a lead body having a lumen extending the length thereof and capable of receiving a stylet for implantation. This allows a reduced diameter lead to be used. The reduced diameter lead body is electrically coupled to the electrode assembly. The reduced diameter lead body may include a cable or coil conductor and an insulator covering same. The electrode assembly may be of a passive fixation or an active fixation design. If the electrode assembly uses passive fixation, the assembly may include at least one tine to fix the electrode at a target location. If the electrode assembly uses active fixation, the assembly may include a screw helix.
The method for implanting a lead conforming to the second aspect of the present invention also includes a guide catheter and a pushing stylet. The distal end of the guide catheter is positioned at a target location within the heart of a patient. The guide catheter may include a radio-opaque coating or marker bands allowing the catheter to be visualized during positioning using fluoroscopy, magnetic resonance imaging, echocardiography, or by other methods known to those skilled in the art. The distal end of the pushing stylet is inserted into the cavity at the proximal end of an electrode assembly. This frictionally secures the electrode assembly to the pushing stylet. The pushing stylet and electrode assembly are then inserted through the proximal end of the guide catheter and advanced through the catheter to the target location at the catheter""s distal end by pushing on the stylet. The catheter is brought into contact with the target location and is secured to the location.
The pushing stylet is then removed from the electrode assembly""s cavity. The pushing stylet may be removed from the electrode using a removal catheter. The removal catheter is inserted through the proximal end of the guide catheter. The removal catheter is passed through the guide catheter until the distal end of the removal catheter abuts the proximal end of the electrode. A stabilizing force is applied to the distal end of the electrode assembly by the removal catheter allowing the user to dislodge the pushing stylet from the cavity without displacing the electrode assembly. The pushing stylet, the guide catheter and the removal catheter are then removed from the patient.
In a third aspect of the invention, the lead includes an electrode assembly having a flange at its proximal end and a reduced diameter lead body. The flange is configured to be secured within the distal end of a guide catheter. The guide catheter""s distal end may include a receiving cavity adapted to receive the flange. Securing the electrode in the catheter""s distal end allows the guide catheter to transport the electrode assembly to a target location in the heart without use of a stylet wire. The reduced diameter lead body is electrically coupled to the electrode assembly. The reduced diameter lead body may include a cable or coil conductor and a cover insulator. The electrode assembly may be of a passive fixation or an active fixation design. If the electrode assembly uses passive fixation, the assembly may include at least one tine to fix the electrode at a target location. If the electrode assembly uses active fixation, the assembly may include a screw helix.
The method for implanting a lead conforming to the third aspect of the present invention includes a guide catheter and a removal stylet. The flange of the electrode assembly is secured to the distal end of the catheter. The distal end of the guide catheter and the electrode assembly are advanced through a blood vessel with the electrode assembly being positioned at a target location within the heart of a patient.
The guide catheter can be of the peel-away variety or may take other forms that will be recognized by those skilled in the art. It may also include a radio-opaque coating, allowing the catheter to be visualized during positioning using fluoroscopy, magnetic resonance imaging, echocardiography, or by other methods known to those skilled in the art. The electrode assembly is secured at the target location. Either prior to or after the electrode assembly is secured, a removal stylet is then inserted into the proximal end of the guide catheter and passed through the guide catheter until its distal end comes into contact with the proximal end of the electrode assembly. The removal stylet can be used to apply a force to the distal end of the electrode assembly to simply detach the flange on the electrode assembly from the guide catheter or it can additionally cooperate with a cavity in the proximal end of the electrode assembly to actively fix the electrode. Alternatively, the electrode assembly of a type having a corkscrew tip is secured to the target location by rotating a proximal end of the guide catheter prior to detaching the electrode assembly from the distal end of the guide catheter. After the electrode assembly is secured and the electrode assembly is removed, the catheter and the removal stylet are withdrawn from the patient.
In addition, upon review of the following disclosure, those skilled in the art will recognize additional aspects, advantages and improvements conferred by the present invention.